HeapFileEncoder reads a comma delimited text file or accepts
an array of tuples and converts it to
pages of binary data in the appropriate format for simpledb heap pages
Pages are padded out to a specified length, and written consecutive in a
data file.

The format of the log file is as follows:
The first long integer of the file represents the offset of the
last written checkpoint, or -1 if there are no checkpoints
All additional data in the log consists of log records.